Massive giant planets found in star cluster

London: Scientists have discovered unexpectedly high number of giant exoplanets in a cluster of stars called Messier 67 that is about the same age as the Sun — indicating that our solar system might have arisen in a similarly dense environment. The team used several telescopes and instruments, including the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph at European Southern Observatory’s La Silla centre in Chile, to collect high-precision measurements of 88 stars in Messier 67.

“We want to use an open star cluster as laboratory to explore the properties of exoplanets and theories of planet formation”, said Roberto Saglia from the Max Planck Institutes in Germany who led the team. “Here we have not only many stars possibly hosting planets, but also a dense environment, in which they must have formed,” Saglia added. The study, published in the journal Astronomy and Astrophysics, found that hot Jupiters were more common around stars in Messier 67 than is the case for stars outside of clusters.

A hot Jupiter is a giant exoplanet with a mass of more than about a third of Jupiter’s mass. They are “hot” because they orbit close to their parent stars, as indicated by an orbital period (their “year”) that is less than 10 days in duration. “This is really a striking result,” said Anna Brucalassi, who carried out the analysis. “The new results mean that there are hot Jupiters around some 5 per cent of the Messier 67 stars studied — far more than in comparable studies of stars not in clusters, where the rate is more like 1 per cent,” Brucalassi added. –IANS